A battery system having a high output voltage by connecting a plurality of battery cells in series is used for supplying power to electric equipment devices such as a motor or a starter of an electric vehicle, a car navigation, or an audio. In a state where the temperature or the voltage of the battery is out of the range of normal and safe usage, normal operation is not kept, and then there is a possibility that degradation of life, or the battery with smoking or burning might occur. Therefore, it is important for keeping a safety to monitor temperature or voltage of the battery. Additionally, in a safety monitoring of the battery system, when an abnormal state of the battery temperature is detected, it is necessary to immediately perform an operation such as turning off a relay connected to an output side. Therefore, it is also important to detect the abnormal state of the battery temperature. Thus, the battery is required to quickly detect the temperature or the voltage of the battery.
The battery system where the battery temperature is detected by the temperature sensor for detecting the temperature of the battery, has been developed. (refer to patent literature 1)